Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 46: Poster 2
HL 46.7: Poster
Thursday, March 29, 2007, 15:00–17:30, Poster A
Photo-electric properties of 4H- and 6H-SiC investigated by resonant SCW excitation — •Burkhard Hilling1, Michaela Lemmer1, Mirco Imlau1, Manfred Wöhlecke1, and Mikhail Petrov2 — 1Department of Physics, University of Osnabrück, Germany — 2Ioffe Physico-Technical Institute, St. Peterburg, Russia
Polytypes of 4H- and 6H-SiC have been investigated with the non-linear phenomenon of resonant space-charge
wave (SCW) excitation at a wavelength of λ = 488 nm. SCW are eigenmodes of spatial-temporal oscillations
of a space-charge density appearing in semi-insulating semiconductors in an external electric field.
SCW excitation was performed with an oscillating interference pattern with a frequency of
10 ≤ Ω ≤ 3000 Hz and an externally applied electric
field E0 up to 9 kV/cm. Resonant excitation was found if Ω equals the eigenfrequency of the generated SCW mode.
Both amplitude and frequency of the resonance depend primarily on the applied electric field E0 and the spatial
frequency K of the interference pattern.
We show that the experimentally obtained dependences on K, E0 and Ω are in good agreement with the
theoretical concept for so-called low-frequency SCW (trap recharging waves). This enables us to determine important
material properties from the analysis for both SiC polytypes. These are the effective trap density
Neff, the product of mobility and lifetime µτ of the photo-excited charge carriers, and the maxwell
relaxation time τM. Strengths and disadvantages of SCW excitation for purposes of semiconductor analysis are
discussed.
Supported by the DFG (projects GRK 695 and 436 RUS 17/15/07)